[css-anchor-1][editorial] Add note making it clearer that non-none fallback prevents anchor(auto) from creating fallback entries. w3c#7757

Author: tabatkins

css-anchor-1/Overview.bs

@@ -321,6 +321,18 @@ consisting of two entries:
 	and the ''anchor()/auto''/''auto-same'' keywords
 	resolved to the opposite sides as well.
 
+Note: If the element has a non-none 'position-fallback',
+these extra entries aren't added.
+Since the [=position fallback list=] styles
+override the "base" styles immediately,
+this will <em>usually</em> mean you wouldn't see a "base" ''anchor(auto)''
+show up in the final styles at all,
+but if that does happen
+(it's specified in a property
+that isn't overriden by anything in the [=position fallback list=]),
+the only effect of the ''anchor()/auto''/''auto-same''
+is to resolve to the appropriate side keyword.
+
 <div class=example>
 	For example, the following code using [=automatic anchor positioning=]:
 
@@ -364,6 +376,7 @@ as specified above,
 if they would validly trigger [=automatic anchor positioning=].
 
 
+
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